In general the invention relates to the handling and processing of sheet materials, and more particularly to apparatus for hanging such sheets from an upper edge thereof during processing, transporting and storage.
The handling of relatively large sheet material, especially heavy metal sheets, such as the aluminum skin sections used to construct the body of an aircraft, involves numerous problems in supporting and moving the sheets from the initial milling operation through the various downstream processing stages. Such downstream operations may, for example, include shot peening, electroprocessing, painting and curing. To efficiently schedule these processing operations, it is necessary to store the sheets temporarily between processes and, hence, the sheet material must be frequently moved to the storage locations and retrieved therefrom quickly and efficiently without damaging the partially processed sheet.
Heretofore, heavy metal sheets of relatively large planar dimensions, have been handled by attaching inverted U-brackets, each with a shear bolt and wing nut, to holes provided at spaced locations along the upper edge of the sheet. The brackets are in turn supported from above by steel cables that depend downwardly from rachet drums and that are looped through the inverted U-bracket. These U-brackets, steel cables and rachet drums are however not capable of constraining the sheet to a planar configuration, and twisting of the cables and the brackets has frequently resulted in buckling of the sheet along the supported edge. Sheet buckling sometimes caused permanent deformation to the skin section, and in other cases hindered uniform treatment of the skin faces such as when they were painted by the use of automatic spray guns. Furthermore, to store the sheets between processing stages, it has been necessary to lower the sheets between stanchions and rest the lower sheet edges on bottom stops, subjecting the sheets, especially the lower edges thereof, to scratching, galling and other surface damage. Also, the inverted U-brackets cannot in all cases be left on the partially processed sheet, and removal and reattachment of the bracket bolts required significant operator time.
When the sheet material, such as the aluminum skins for an aircraft body, requires electroplating or anodizing as one of the processes, the inverted U-brackets, cables and rachet drums have been used to support the sheet in the electrochemical bath, and separate clamping electrodes have been attached to the sheet to apply the necessary electrical potential thereto. To first attach, and then after the electroprocessing, disconnect the separate electrodes, added undue delay to the electroprocessing operation. Moreover, the rachet drum cables used to support the U-shaped brackets were made of steel in order to provide needed strength and flexibility, and the electrochemicals used during the sheet anodizing operations quickly corroded the cables, making them difficult to use and required frequent replacement.
Accordingly, an object of the invention is to provide a device for hanging sheet material from an upper edge thereof during multistep processing of the sheet material wherein the device is quickly attachable and detachable from the sheet, and is capable of supporting the sheet from an overhead hoist or the like, and is equally capable of supporting the sheet in downwardly depending relation from a pair of elevated and spaced parallel rails.
A further object of the invention is to provide such a sheet hanging device, made of an electrically conductive metal, and incorporating a screw clamp that is used during electroprocessing of a metal sheet material, to force the sheet into positive electrical contact with the body of the hanging device for applying the necessary electrical charge to the sheet through such device, and is itself constructed so as to resist damage due to electrochemical corrosion.
Still another object of the invention is to provide such a hanging device having the capability of being attached, along with a plurality of like hanging devices, to a sheet of material, at an early stage of successive processing steps for use in transporting the sheet to and from each processing station, and for storing the sheet between processing stages.
An additional object is to provide a hanger device, capable of cooperating with a plurality of like hanger devices so that when attached to an upper edge of a relatively large and flexible sheet of material, the hanger devices constrain the sheet to a generally planar configuration to resist buckling of the sheet.